Saint Isaac's Cathedral or Isaakievskiy Sobor (Russian: Исаа́киевский Собо́р) in Saint Petersburg, Russia is the largest Russian Orthodox cathedral (sobor) in the city. It is the largest orthodox basilica and the fourth largest (by the volume under the cupola) cathedral in the world. It is dedicated to Saint Isaac of Dalmatia, a patron saint of Peter the Great, who had been born on the feast day of that saint.